This standard specifies the method for determining the content of glycoside hydrocyanic acid in beans. This standard is applicable to the determination of glycoside hydrocyanic acid in beans. GB/T 15665-1995 Determination of glycoside hydrocyanic acid content in beans GB/T15665-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of glycosidic hydrocyanic acid
Pulses-Determination of glycosidic hydrocyanic acidGB/T15665-1995
This standard adopts the method of international standard ISO2164:1975 "Beans-Determination of glycosidic hydrocyanic acid". 1 Subject content and scope of application
This standard specifies the method for the determination of glycosidic hydrocyanic acid in beans. This standard is applicable to the determination of glycosidic hydrocyanic acid in beans. 2 Reference StandardsbZxz.net
GB601 Preparation of Standard Solution for Chemical Reagent Titration Analysis (Volume Analysis) 3 Principle
After hydrolysis, the glycoside hydrocyanic acid in beans is steam distilled. The distilled hydrocyanic acid is absorbed by the alkali solution. Potassium iodide is used as an indicator and the hydrocyanic acid is titrated with a standard nitric acid solution. The silver ions first react with the hydrocyanate ions to form a soluble complex [Ag (CN),). When the end point is reached, the excess silver nitrate reacts with the iodide ions to form a continuous turbid precipitate, indicating the end point. The amount of the silver nitrate standard solution consumed is used to calculate the content of hydrocyanic acid.
4 Reagents
All reagents are analytically pure, and water is distilled water or water of equal purity. 4.1 Sodium acetate solution: 2% (W/V), weigh 20g sodium acetate (GB693) and dissolve it in water, adjust the pH to 5.0±0.5 with acetic acid, and add water to 1000mL
4.2 Potassium dihydrogen phosphate solution: 2% (W/V), weigh 20g potassium dihydrogen phosphate (GB1274) and dissolve it in water, dilute to 1000mL. 4.3 Sodium hydroxide solution: 5% (W/V), weigh 50g sodium hydroxide (GB629), dissolve it in water, and dilute to 1000mL. 4.4 Ammonia solution: 6mol/L, measure 400mL ammonia water (GB631), add water and dilute to 1000mL. 4.5 Potassium iodide solution: 5% (W/V), weigh 50g potassium iodide (GB1272), dissolve it in water, and dilute to 1000mL. 4.6 Silver nitrate standard solution: 0.004 mol/L, prepared and calibrated according to GB601. 4.7 Sweet almond.
5 Instruments and equipment
5.1 Steam distillation apparatus: distillation flask 2000~2500mL. 5.2 Kjeldahl flask: 1000mL.
5.3 Conical flask: 250mL.
5.4 Volumetric flask: 250mL.
5.5 Pipette: 100mL.
5.6 Microburette: 10mL.
Approved by the State Administration of Technical Supervision on August 18, 1995 and implemented on June 1, 1996
5.7 Analytical balance: sensitivity 0.0018.
5.8 Ice bath.
GB/T15665—1995
5.9 Crusher: easy to clean, and should not generate high heat during crushing to affect the water content in the sample. 5.10 Sieve: aperture 1mm.
5.11 Incubator: temperature controlled at 38±2℃. 6 Analysis steps
6.1 Selection and preparation of samples
Select representative samples and reduce the sampling by quartering method. The sampling amount shall not be less than 300g. Grind the sample with a crusher (5.9), sieve (5.10), discard the initial small amount of powder sample, and collect the remaining powder sample in a wide-mouth bottle for testing. 6.2 Sample hydrolysis
6.2.1 Hydrolysis method
Weigh 20g sample to the nearest 0.1g, place in a 1000mL Kjeldahl flask (5.2), add 50mL water and 10mL sodium acetate solution (4.1) or potassium dihydrogen phosphate solution (4.2), plug the bottle mouth, mix thoroughly, and place it in a 38℃ incubator (5.11) for hydrolysis for 12h. 6.2.2 Enzyme hydrolysis method
Weigh 20g sample to the nearest 0.1g, place in a 1000mL Kjeldahl flask (5.2), add 1.5~2.0g of 2 crushed sweet almonds (without hydrocyanic acid), add 50mL water, plug the bottle mouth, and place it in a 38℃ incubator for enzymatic hydrolysis for 2h. Note: You can choose either of the two methods 6.2.1 and 6.2.2. The enzymatic hydrolysis method is more suitable for samples with weak enzyme activity. 6.3 Sample distillation
Place the hydrolyzed sample in an ice bath to cool for 15-20 minutes, add 80 mL of water and a drop of defoamer, immediately connect the Kjeldahl flask to the distillation apparatus (5.1), allow the lower end of the condenser to penetrate below the liquid surface of the conical flask (5.3) containing 20 mL of sodium hydroxide solution (4.3), pass steam to distill, and collect 100-150 mL of distillate. When removing the conical flask, rinse the end of the condenser, transfer the distillate to a 250 mL volumetric flask, and make up to volume.
6.4 Titration
Use a pipette (5.5) to take two 100 mL portions of distillate and place them in two conical flasks respectively, add 2 mL of potassium iodide solution (4.5) and 1 ml of ammonia solution (4.4), mix well, and titrate with a silver nitrate standard solution (4.6) against an ink background until a continuous turbid precipitate appears as the end point. 6.5 When titrating with the above procedure, if a light black precipitate or brown precipitate appears, it indicates the presence of S-2 ions. Determine as follows: Pipette two 100 mL portions of distillate into two beakers, add 5 mL of lead nitrate solution (5 g/L) to mix, let stand for 15 min, filter, wash the beaker and filter three times with 10 mL of water each time, then add 2 mL of potassium iodide solution (4.5) and 1 mL of ammonia solution (4.4) to the solution and mix. Titrate with silver nitrate standard solution (4.6). 6.6 Blank determination
Replace the distillate with distilled water and perform a blank test as in 6.4. 7 Calculation of results
7.1 Expression of results
The content of glycosylated hydrocyanic acid is expressed as milligrams of hydrocyanic acid (HCN) per kilogram of sample, calculated as follows: X=Vi-Vo)XcX 54 ×1 000
m X 100/250
Wherein: X—the content of hydrocyanic acid in the sample, mg/kg; V, the volume of silver nitrate standard solution consumed in the sample determination, mLV; c—the volume of silver nitrate standard solution consumed in the blank titration, mL; 54—2 times the molecular weight of hydrocyanic acid;
the mass of the sample, g.
7.2 Expression of analytical results
GB/T 15665--1995
The results of two parallel determinations of the same sample are expressed as the arithmetic mean, accurate to one decimal place. When the result shows that the hydrocyanic acid content per kilogram of sample is less than 10 mg, it can be considered that the sample does not contain glycoside hydrocyanic acid. Additional remarks:
This standard is proposed by the Ministry of Agriculture of the People's Republic of China. This standard is under the jurisdiction of the National Agricultural Analysis Standardization Technical Committee. This standard is drafted by the Analysis and Testing Center of the Chinese Academy of Agricultural Sciences. The main drafters of this standard are Li Yufang and Liu Suyun. 465
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